PAPERS ON BIOLOGY AND AGRICULTURE 177 



its area. These woods also show well a marked feature of 

 most of the Rock River woodlands, that is, the decided in- 

 crease in mesoph}-tism in proceeding from portions back from 

 the river towards portions near the river. This is what 

 might in general be expected on an intrenched valley slope. 

 The physiogi'aphic divei-sity, however, occasions many 

 places where this might not be the case. Nevertheless 

 when the vegetative succession is allowed to proceed with- 

 out disturbance it appears to be quite general. In the 

 Cartwright woods at their western part, that is the portion 

 farthest from the Rock. Quercus macrocai-pa is prominent 

 in the stand. Towards the eastern part this species is al- 

 most lacking. The increase in mesophytism from west to east 

 is shown by the appearance and increase in numbers of such 

 trees as Juglans nigra, J. cinerea, Ulmus americana. On 

 higher and drier parts of the area, mainly at the western 

 portion, Quercus ellipsoidalis is the chief tree. The more 

 mesophjiiic eastern part bears the more mesophytic herbs, 

 although in some small areas westward, where especially 

 favorable conditions prevail on account of the topography, 

 such herbs are also prominent. In one part of these woods 

 there occur old trees of Quercus alba, usually with short 

 bole and much branched form. They are quite the oldest 

 trees of these woods. Their appearance suggests that they 

 have belonged to an older stand that was largely open- 

 grown. Into this older stand, presumably, there came 

 the later, present stand of Quercus ellipsoidalis, Q. velu- 

 tina, Q. alba, Hicoria ovata, and others, from which the 

 still later, more mesophj-tic. phase of the succession has 

 developed. The species of the climax here do not differ 

 materially from the examples of it already described, ex- 

 cept that in these Cartwright woods there is some Betula 

 lutea. This species occurs in a few other places also, being 

 usually present as an expression of certain especially favor- 

 able, very localized habitats, rather than as a regular mem- 

 ber of the oak-maple climax form. 



An extremely mesoph^liic assemblage representative of 

 the moist areas at the heads of small ra\"ines and other simi- 

 larly moist areas is shown at the ravine head on the north 

 slope of Libertj' Hill back of the town of Oregon. Here 



